Note 19 - Business Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Total revenue	$ 1,088,110	$ 1,055,591	$ 2,497,451	$ 2,426,089
Gross profit	91,432	144,491	79,506	281,143
Segment assets	2,633,773	2,643,848	2,633,773	2,643,848	$ 2,476,601
Transportation [Member]
Total revenue	598,646	610,847	1,340,834	1,472,703
Gross profit	13,633	70,976	(64,996)	138,401
Depreciation, depletion and amortization	4,096	7,592	12,581	17,920
Segment assets	314,361	394,981	314,361	394,981
Water [Member]
Total revenue	135,908	124,292	347,994	215,951
Gross profit	15,030	24,103	34,412	41,117
Depreciation, depletion and amortization	9,272	11,191	31,259	16,075
Segment assets	294,211	308,964	294,211	308,964
Specialty [Member]
Total revenue	224,457	190,836	540,234	461,149
Gross profit	38,299	28,099	75,376	65,311
Depreciation, depletion and amortization	7,747	7,569	21,960	18,908
Segment assets	140,192	150,437	140,192	150,437
Materials [Member]
Total revenue	129,099	129,616	268,389	276,286
Gross profit	24,470	21,313	34,714	36,314
Depreciation, depletion and amortization	6,784	6,496	18,417	17,980
Segment assets	367,944	375,016	367,944	375,016
Operating Segments [Member]
Total revenue	1,169,227	1,120,561	2,631,521	2,542,436
Gross profit	91,432	144,491	79,506	281,143
Depreciation, depletion and amortization	27,899	32,848	84,217	70,883
Segment assets	1,116,708	1,229,398	1,116,708	1,229,398
Operating Segments [Member] | Transportation [Member]
Total revenue	598,646	610,847	1,340,834	1,472,703
Operating Segments [Member] | Water [Member]
Total revenue	135,908	124,292	347,994	215,951
Operating Segments [Member] | Specialty [Member]
Total revenue	224,457	190,836	540,234	461,149
Operating Segments [Member] | Materials [Member]
Total revenue	210,216	194,586	402,459	392,633
Consolidation, Eliminations [Member]
Total revenue	(81,117)	(64,970)	(134,070)	(116,347)
Consolidation, Eliminations [Member] | Transportation [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Water [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Specialty [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Materials [Member]
Total revenue	$ (81,117)	$ (64,970)	$ (134,070)	$ (116,347)